Semiconductor Physics, Quantum Electronics & Optoelectronics, 23 (2), P. 146-154 (2020).

Dielectric properties of nematic liquid crystal with impurities of supramolecular Ni-TMTAA-TCNQ complexes
V.E. Vovk1, O.V. Kovalchuk1,2,3, P. Kopčanský4, T.M. Kovalchuk5

1Institute of Physics, NAS of Ukraine 46, prospect Nauky, 03680 Kyiv, Ukraine
2Kyiv National University of Technologies and Design, 2, Nemirovich-Danchenko str., 01011 Kyiv, Ukraine
3National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute” 37, prospect Peremohy, 03056 Kyiv, Ukraine
4Institute of Experimental Physics, Slovak Academy of Sciences 47, Watsonova str., 04001 Košice, Slovakia
5V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine 41, prospect Nauky, 03680 Kyiv, Ukraine E-mail:

Abstract. Within the temperature range 288–343 K and frequencies 10–1–106 Hz, the dielectric properties of planar and homeotropic oriented nematic liquid crystal 6CHBT with the impurity of 0–3 wt.% Ni-TMTAA-TCNQ molecules have been investigated. It has been shown that at the lowest frequencies, the dispersion of components of the complex dielectric permittivity in the case of a planar oriented liquid crystal is caused by oscillations of molecular dipoles within the range of angles corresponding to fluctuations of the order parameter under the action of electric field. The values of relaxation times have been estimated, and it has been shown that with the increase in the impurity concentration, the value of the relaxation time decreases. The temperature dependences of the values inverse to the relaxation time have been analyzed. It has been shown that for the middle frequency range the obtained dielectric spectra characterize the bulk properties of the samples, in particular the value of the electrical conductivity. It has been found that with increasing the molecular concentration, the activation energy for the temperature dependence of the electrical conductivity increases. This dependence for the whole range of studied temperatures correlates with the temperature dependence of the values inverse to the relaxation time. It has been shown that at the concentration of the impurity up to 1 wt.%, the conductivity of the samples both in homeotropic and planar orientations of molecules varies according to the power law of the impurity concentration. It has been estimated the value of the exponent for the concentration dependence of conductivity, and it has been shown that it is the same for various molecular orientations.

Keywords: ielectric properties, nematic liquid crystal, planar and homeotropic orientation of molecules, relaxation time, activation energy, molecular complexes Ni-TMTAA-TCNQ.

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